Cellular oncogenes are believed to play a role in normal cell proliferation and/or differentiation. In addition evidence exists linking adherent expression of these genes to malignant transformation. We have demonstrated that the cellular oncogenes: c-abl, c-erb, c-fos, c-myc, c-ras[unreadable]Ha[unreadable], c-src, and c-sis are all expressed during murine embryogenesis. Five of these genes; c-abl, c-fos, c-myc, c-ras[unreadable]Ha[unreadable] and c-src were expressed in a time related and/or tissue specific fashion during embryogenesis. The expression of cellular oncogenes was determined by analysis of mRNA obtained from whole mouse embryos at various stages of development. This approach does not identify the specific tissues responsible for the bulk of expression of a given cellular oncogene. For this reason we are developing histochemical techniques to clarify the issue. We are also studied cellular oncogene expression in a large survey of 53 human malignancies representing 20 different tumor types and found expression of c-fos, c-myc, c-ras[unreadable]Ha[unreadable] and c-ras[unreadable]Ki[unreadable] in all tumors. The c-abl, c-fes, c-fms and c-myb genes were expressed in certain tumors. Given the strong association of the c-myb oncogene with human leukemia we obtained a c-DNA clone of this gene from fresh human leukemic blasts and expressed this clone in a bacterial expression. The expressed fusion protein was used as an immunogen to develop specific anti-myb antisera. A similar approach was taken with the c-fos gene product and given us specific antisera for this product. (X)